1/* vi: set sw=4 ts=4: */ 2/* 3 * Russ Dill <Russ.Dill@asu.edu> July 2001 4 * 5 * Licensed under GPLv2, see file LICENSE in this source tree. 6 */ 7#include "common.h" 8#include "dhcpd.h" 9 10/* Find the oldest expired lease, NULL if there are no expired leases */ 11static struct dyn_lease *oldest_expired_lease(void) 12{ 13 struct dyn_lease *oldest_lease = NULL; 14 leasetime_t oldest_time = time(NULL); 15 unsigned i; 16 17 /* Unexpired leases have g_leases[i].expires >= current time 18 * and therefore can't ever match */ 19 for (i = 0; i < server_config.max_leases; i++) { 20 if (g_leases[i].expires < oldest_time) { 21 oldest_time = g_leases[i].expires; 22 oldest_lease = &g_leases[i]; 23 } 24 } 25 return oldest_lease; 26} 27 28/* Clear out all leases with matching nonzero chaddr OR yiaddr. 29 * If chaddr == NULL, this is a conflict lease. 30 */ 31static void clear_leases(const uint8_t *chaddr, uint32_t yiaddr) 32{ 33 unsigned i; 34 35 for (i = 0; i < server_config.max_leases; i++) { 36 if ((chaddr && memcmp(g_leases[i].lease_mac, chaddr, 6) == 0) 37 || (yiaddr && g_leases[i].lease_nip == yiaddr) 38 ) { 39 memset(&g_leases[i], 0, sizeof(g_leases[i])); 40 } 41 } 42} 43 44/* Add a lease into the table, clearing out any old ones. 45 * If chaddr == NULL, this is a conflict lease. 46 */ 47struct dyn_lease* FAST_FUNC add_lease( 48 const uint8_t *chaddr, uint32_t yiaddr, 49 leasetime_t leasetime, 50 const char *hostname, int hostname_len) 51{ 52 struct dyn_lease *oldest; 53 54 /* clean out any old ones */ 55 clear_leases(chaddr, yiaddr); 56 57 oldest = oldest_expired_lease(); 58 59 if (oldest) { 60 memset(oldest, 0, sizeof(*oldest)); 61 if (hostname) { 62 char *p; 63 64 hostname_len++; /* include NUL */ 65 if (hostname_len > sizeof(oldest->hostname)) 66 hostname_len = sizeof(oldest->hostname); 67 p = safe_strncpy(oldest->hostname, hostname, hostname_len); 68 /* 69 * Sanitization (s/bad_char/./g). 70 * The intent is not to allow only "DNS-valid" hostnames, 71 * but merely make dumpleases output safe for shells to use. 72 * We accept "0-9A-Za-z._-", all other chars turn to dots. 73 */ 74 while (*p) { 75 if (!isalnum(*p) && *p != '-' && *p != '_') 76 *p = '.'; 77 p++; 78 } 79 } 80 if (chaddr) 81 memcpy(oldest->lease_mac, chaddr, 6); 82 oldest->lease_nip = yiaddr; 83 oldest->expires = time(NULL) + leasetime; 84 } 85 86 return oldest; 87} 88 89/* True if a lease has expired */ 90int FAST_FUNC is_expired_lease(struct dyn_lease *lease) 91{ 92 return (lease->expires < (leasetime_t) time(NULL)); 93} 94 95/* Find the first lease that matches MAC, NULL if no match */ 96struct dyn_lease* FAST_FUNC find_lease_by_mac(const uint8_t *mac) 97{ 98 unsigned i; 99 100 for (i = 0; i < server_config.max_leases; i++) 101 if (memcmp(g_leases[i].lease_mac, mac, 6) == 0) 102 return &g_leases[i]; 103 104 return NULL; 105} 106 107/* Find the first lease that matches IP, NULL is no match */ 108struct dyn_lease* FAST_FUNC find_lease_by_nip(uint32_t nip) 109{ 110 unsigned i; 111 112 for (i = 0; i < server_config.max_leases; i++) 113 if (g_leases[i].lease_nip == nip) 114 return &g_leases[i]; 115 116 return NULL; 117} 118 119/* Check if the IP is taken; if it is, add it to the lease table */ 120static int nobody_responds_to_arp(uint32_t nip, const uint8_t *safe_mac, unsigned arpping_ms) 121{ 122 struct in_addr temp; 123 int r; 124 125 r = arpping(nip, safe_mac, 126 server_config.server_nip, 127 server_config.server_mac, 128 server_config.interface, 129 arpping_ms); 130 if (r) 131 return r; 132 133 temp.s_addr = nip; 134 bb_info_msg("%s belongs to someone, reserving it for %u seconds", 135 inet_ntoa(temp), (unsigned)server_config.conflict_time); 136 add_lease(NULL, nip, server_config.conflict_time, NULL, 0); 137 return 0; 138} 139 140/* Find a new usable (we think) address */ 141uint32_t FAST_FUNC find_free_or_expired_nip(const uint8_t *safe_mac, unsigned arpping_ms) 142{ 143 uint32_t addr; 144 struct dyn_lease *oldest_lease = NULL; 145 146#if ENABLE_FEATURE_UDHCPD_BASE_IP_ON_MAC 147 uint32_t stop; 148 unsigned i, hash; 149 150 /* hash hwaddr: use the SDBM hashing algorithm. Seems to give good 151 * dispersal even with similarly-valued "strings". 152 */ 153 hash = 0; 154 for (i = 0; i < 6; i++) 155 hash += safe_mac[i] + (hash << 6) + (hash << 16) - hash; 156 157 /* pick a seed based on hwaddr then iterate until we find a free address. */ 158 addr = server_config.start_ip 159 + (hash % (1 + server_config.end_ip - server_config.start_ip)); 160 stop = addr; 161#else 162 addr = server_config.start_ip; 163#define stop (server_config.end_ip + 1) 164#endif 165 do { 166 uint32_t nip; 167 struct dyn_lease *lease; 168 169 /* ie, 192.168.55.0 */ 170 if ((addr & 0xff) == 0) 171 goto next_addr; 172 /* ie, 192.168.55.255 */ 173 if ((addr & 0xff) == 0xff) 174 goto next_addr; 175 nip = htonl(addr); 176 /* skip our own address */ 177 if (nip == server_config.server_nip) 178 goto next_addr; 179 /* is this a static lease addr? */ 180 if (is_nip_reserved(server_config.static_leases, nip)) 181 goto next_addr; 182 183 lease = find_lease_by_nip(nip); 184 if (!lease) { 185//TODO: DHCP servers do not always sit on the same subnet as clients: should *ping*, not arp-ping! 186 if (nobody_responds_to_arp(nip, safe_mac, arpping_ms)) 187 return nip; 188 } else { 189 if (!oldest_lease || lease->expires < oldest_lease->expires) 190 oldest_lease = lease; 191 } 192 193 next_addr: 194 addr++; 195#if ENABLE_FEATURE_UDHCPD_BASE_IP_ON_MAC 196 if (addr > server_config.end_ip) 197 addr = server_config.start_ip; 198#endif 199 } while (addr != stop); 200 201 if (oldest_lease 202 && is_expired_lease(oldest_lease) 203 && nobody_responds_to_arp(oldest_lease->lease_nip, safe_mac, arpping_ms) 204 ) { 205 return oldest_lease->lease_nip; 206 } 207 208 return 0; 209} 210